Plugboards or interconnect systems as disclosed in U.S. Pat. Nos. 2,927,295 and 3,133,775 were used to internally program computer functions and, in test equipment, were used to create input/output interfaces. The plugboard programming system and front panel interconnect provided infinite switching combinations through use of permanently-wired rear boards and selectively-programmed front boards.
The present problem is that logic systems have shrunk to typically 0.100 inch centerlines, whereas plugboards have been limited to 0.250 or 0.375 inch contact centers. Using these plugboards in the current 0.100 inch centerline logic systems has meant that interconnects must be hand-wired thereby resulting in a complicated wiring maze and signal degradation due to varying impedances, crosstalk, and excessive lead lengths. Also, in the old plugboard interface, separate power and ground input/output were relied upon.
These factors, combined with the unwieldy size of plugboards and their vulnerable exposed contacts required a new kind of plugboard system in order to accommodate the new generation of automatic test equipment that has been developed.
According to the present invention, a high density interconnect system comprises a laminated interface board including a power plane and a ground plane insulated from each other and through which a series of holes extend, preferably at a spacing of 0.100 inches. Signal contacts, ground contacts, power contacts, data bus interconnect contacts, and feed-through contacts are selectively mounted in the series of holes with the ground contacts and power contacts connected to the respective ground and power planes while the other contacts are insulated therefrom. Front contact housings are secured against the laminated interface board and contain spring-loaded contacts in openings therein for electrical engagement with the signal contacts and for electrical engagement with pins of a signature board. Rear contact housings house contact sections of the signal, power, ground, and data bus interconnect contacts to which input/output connectors of computer boards are connected for supplying power thereto and operating signals are supplied by the computer boards to the signature board which conducts tests on the board under test to test same. A cam-operating apparatus moves a platen carrying the signature board so that the pins of the signature board are moved into electrical engagement with the spring-loaded contacts.